There is a constant demand for the addition of makeup water into a swimming pool or spa. Summertime pool of spa use is usually high and splashout causes large losses of treated, balanced water which then requires the addition of makeup water. Wintertime water losses are also extremely high due to evaporation. Summertime makeup water requires the addition of chemicals because of their loss with the water splashout. Wintertime makeup water does not require the addition of chemicals because the chemicals in the pool were not lost with the evaporating water. Most makeup water is added, unfiltered and untreated, into the pool or spa by dropping a garden hose into the vessel and turning it on. There are no desirable, balanced water sources as is, for introduction as makeup water into a pool or spa. Both city and well water contains some combination of sand, silt, clay, gases, algae, bacteria, viruses, other organics or metals in a ferrous or ferric state. Alone or in combination these contaminants cause stains on pool and spa finishes. These containments also create a demand on the pool or spas free available chlorine residual. As the free available chlorine residual is reduced the pool or spa water becomes prone to algae blooms and bacteria growth. The algae and bacteria growth requires the introduction of large amounts of extra chemicals to kill it, in order to prevent bathers from getting sick and/or infections.
A garden hose lying on the bottom of the pool or spa when filling or adding makeup water will leave either a stain or rough mark on the finish. This is caused by the abrupt change to the waters saturation index against the finish. Pool or spa water must be kept in a state of balance or it becomes either aggressive and eats the finish, or it becomes alkaline and will precipitate calcium or silica out of the water and onto the surface finish. Aggressive makeup water from the hose against the finish either dissolves the finish leaving a small rough crater or dissolves some of the copper out of the hose end which then is quickly deposited as a blue stain onto the finish. Alkaline makeup water from the hose against the finish causes a rough spot in the finish due to either calcium precipitate (which can be removed with muriatic acid), or silica precipitate (which cannot be removed without damaging the finish).
In order to prevent the finish problems that occur due to the garden hose against the bottom, the hose should be held at least twelve inches off of the bottom of the pool or spa and at least twelve inches away from any side.